Studies will be directed toward the in vitro cultivation of Treponema pallidum. The lipid metabolism (phospholipid and neutral lipid) of cultivated treponemes will be studied as well as the utilization and alteration of free long chain fatty acids. The mechanism and compounds used in a commensal culture system involving two different species of treponemes with lipid composition similar to T. pallidum will also be investigated. The stimulatory compound or compounds will be isolated and identified. All information on lipid metabolism studies of cultivated treponemes will be used in experiments designed to grow T. pallidum.